In general, a saddle-type fuel tank is provided with two level gauges, that is, a main fuel level sensor and a sub fuel level sensor, and the two level sensors are utilized to measure the fuel level.
However, such a saddle-type fuel system has a problem in that the state of the wires connecting the two level sensors is not accurately diagnosed, therefore the disconnection or short circuit of the wires between the two level sensors cannot be detected. In particular, in North America, the diagnosis of the leakage of evaporated gas and misfires in a fuel system is essential according to OBD-2 regulations. For this purpose, the values detected by fuel level sensors are essentially required for the determination of the amount of fuel, so that monitoring the connection states of wires between fuel level sensors is also essential.
Accordingly, the inventor of the present invention recognizes the necessity of monitoring the connection states of wires between two level sensors provided in a saddle-type fuel system, and has put forth this proposal.